1. Field of the Invention
The present invention relates to a light emitting display and a driving method thereof, and more particularly, to a light emitting display and a driving method thereof, in which an emitting period of a light emitting device is partially shortened to limit brightness, so that light emitted from the light emitting device is prevented from exceeding in brightness, and a power supply is protected from being overloaded.
2. Discussion of Related Art
Recently, various flat panel displays have been developed to substitute for a cathode ray tube (CRT) display because the CRT display is relatively heavy and bulky. The flat panel display includes a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), a light emitting display (LED), etc.
Among the flat panel displays, the light emitting display can emit light for itself by electron-hole recombination. The light emitting display can be classified according to materials into an inorganic light emitting display including an inorganic emitting layer and an organic light emitting display including an organic emitting layer. The light emitting display may also be referred to as an electroluminescent display.
Like a CRT display, such a light emitting display has a fast response time as compared with an LCD display that requires a separate light source.
As for the light emitting display, the organic light emitting display has an organic light emitting device including an organic emitting layer provided between an anode electrode and a cathode electrode, an electron transport layer, and a hole transport layer. Additionally, the organic light emitting device may include an electron injection layer and a hole injection layer.
In the organic light emitting device, when a voltage is applied between the anode electrode and the cathode electrode, electrons generated from the cathode electrode are moved to the emitting layer via the electron injection layer and the electron transport layer, and holes generated from the anode electrode are moved to the emitting layer via the hole injection layer and the hole transport layer. Then, the electrons from the electron transport layer and the holes from the hole transport layer are recombined in the emitting layer, thereby emitting light.
Such a conventional light emitting display displays an image by controlling the brightness of the light emitting device on the basis of the amount of current corresponding to a data signal. At this time, the conventional light emitting display receives the current from a power supply so as to control the light emitting device to emit light. Here, the power supply is designed on the basis of a current required when a white signal is displayed on a predetermined area of an image displaying part in a normal black mode. Thus, current consumption increases as the brightness of the image displaying part increases.
In the conventional light emitting display, when the high brightness of an image displayed on the image displaying part continues for a relatively long time, the power supply is overloaded, thereby damaging electric components and electronic components. Consequently, in a case where the brightness of the image displaying part requires current higher than the maximum current that the power supply is designed to provide, a problem arises in that the power supply is not only deteriorated in performance and driving efficiency but also operates abnormally or does not operate.
Further, in the conventional light emitting display, the light is excessively emitted in proportion to an area corresponding to the light emitting device which is turned on, so that the brightness of the light emitting devices is wastefully increased, thereby increasing power consumption and reducing the lifespan of the light emitting device.